Copper nanowires promise cheap, flexible screens

Staff writer, 2nd June 2010

Imagine a foldable iPad: it's perfectly possible, say Duke University scientists, who have found a simple way to make tiny copper nanowires in quantity.

The cheap conductors are small enough to be transparent, making them ideal for thin-film solar cells, flat-screen TVs and computers, and flexible displays, they say.

At present, flat-panel TVs and computer screens rely on a transparent conductive layer made from indium tin oxide (ITO). ITO is also used as a transparent electrode in thin-film solar cells.

But ITO is brittle, so can't be used for flexible screens, it's hard to produce, and it's getting increasingly expensive.

"If we are going to have these ubiquitous electronics and solar cells, we need to use materials that are abundant in the earth's crust and don't take much energy to extract," says Duke assistant professor of chemistry Benjamin Wiley.

He points out that there are very few materials that are known to be both transparent and conductive, which is why ITO is still being used despite its drawbacks.

But copper nanowires perform better than carbon nanotubes, and are much cheaper than silver nanowires, Wiley said.

Wiley and his team grew copper nanowires in a water-based solution.
"By adding different chemicals to the solution, you can control the assembly of atoms into different nanostructures," Wiley said.

Because the process is water-based, and because copper nanowires are flexible, Wiley thinks the nanowires could be coated from solution in a roll-to-roll process, like newspaper printing, which would be much more efficient than the ITO production process.

Wiley, who has applied for a patent for his process, expects to see copper nanowires in commercial use in the not-too-distant future. He notes that there is already investment financing available for the development of transparent conductors based on silver nanowires.

"We think that using a material that is a hundred times cheaper will be even more attractive to venture capitalists, electronic companies and solar companies who all need these transparent electrodes," he said.